How to Set up tinc, a Peer-to-Peer VPN

Virtual Private Networks (VPN) are an essential part of any serious network security deployment plan. There are many open-source VPN options but one of them shines above the others: tinc. All VPNs behave as a secure tunnel between two points, but tinc stands out for its “Peer-to-Peer” design. The design allows tinc users a great deal of flexibility, especially when planning a mesh-type network.

From a clear two-server connection to complex mesh private network, this guide will show you how to configure tinc VPN in three different use-case scenarios.

Before You Begin

You will need at least two Linodes for this guide. Complete the following steps for each one:

1. Complete the Getting Started guide.

2. Follow the Setting Up and Securing a Compute Instance guide to create a standard user account, harden SSH access and remove unnecessary network services.

   This guide will use sudo wherever possible. Please ensure you have access to privileged user rights.

3. Update your packages:

   sudo apt update && sudo apt upgrade
   

Basic Setup: Two Node tinc VPN

A typical use case for a two-node tinc is web-based invoicing software, where the database should be on a separate server (for security and disaster recovery), and needs to communicate sensitive data to the application server through the internet. This is a straightforward setup involving only two instances, an application server (which we’ll call appserver) and a database server (dbserver). Each instance will run on a separate Linode:

Gather Network Information

Before getting started, it’s a good idea to make a cheat sheet for yourself listing each node’s public IPv4 address, desired VPN address, VPN network name designation, and tinc-daemon name. The VPN address can be an arbitrary private network IPv4 address, the only rule to follow (if you want to avoid extra routing work) is that they must have the same network prefix, just like a typical LAN. VPN and daemon names must be unique and can’t contain any spaces or special symbols. For the current use case, the following information will be used for tinc configuration:

Install tinc VPN on Ubuntu 16.04

Ubuntu 16.04 will be used for all of the Linodes in this guide. At the time of this writing, the latest stable version of tinc is 1.0.33. Ubuntu’s repositories use an older version, so you will have to build from source:

1. Install the necessary dependencies for building tinc:

   sudo apt install build-essential automake libssl-dev liblzo2-dev libbz2-dev zlib1g-dev
   

2. Get the latest version of tinc from the developer’s site:

   wget https://tinc-vpn.org/packages/tinc-1.0.33.tar.gz
   

3. Extract the archive in a temporary folder:

   tar -xf tinc-1.0.33.tar.gz
   

4. Compile tinc on your system:

   cd tinc-1.0.33
   ./configure --prefix=
   make
   sudo make install
   

Create VPN Working Directory

You can implement as many tinc networks as you need as long as you create a unique working directory for each one (gaming VPN, backups VPN, etc). The name of the folder must match the designated name for your VPN, in this case: linodeVPN. You also need to use the same structure across the servers, which means you need to create the working directory on both:

sudo mkdir -p /etc/tinc/linodeVPN/hosts

Create Configuration Files

You will be required to set up a main configuration file titled tinc.conf on each server. The default location for this file is the root of the working directory.

1. Let’s start with the application server’s file:

   File: /etc/tinc/linodeVPN/tinc.conf

   1 2 3

   Name = appserver Device = /dev/net/tun AddressFamily = ipv4

   • Name - This is a daemon-specific name within the VPN. It should be unique.
   • Device - Determines the virtual network to use. Tinc will automatically detect what kind of device you are using.
   • AddressFamily - Tell tinc which type of address to use.

2. Now you need to generate the database server’s configuration file:

   File: /etc/tinc/linodeVPN/tinc.conf

   1 2 3 4

   Name = dbserver Device = /dev/net/tun AddressFamily = ipv4 ConnectTo = appserver

   ConnectTo - This value points to the tinc daemon you want to connect. When it’s not present (like in the previous file), tinc enters listening mode and waits for connections.

   Note

   You can customize tinc behavior with many other parameters in the configuration file, for more information visit the tinc documentation.

3. Create the hosts configuration file. Because tinc is built using a peer-to-peer model each node needs to communicate with the others. The basic host file for the application server is:

   File: /etc/tinc/linodeVPN/hosts/appserver

   1 2	Address = 11.11.11.11 Subnet = 192.168.100.209

4. Similarly, create a host file for Database Server:

   File: /etc/tinc/linodeVPN/hosts/dbserver

   1 2	Address = 22.22.22.22 Subnet = 192.168.100.130

5. Add the public key of each node. tinc can create the key pair using the following command:

   sudo tincd -n linodeVPN -K 4096
   

   For this example we’re using 4096-bit encryption, you can choose a higher level if necessary. Save both rsa_key.pub and rsa_key.priv to the root of your working directory, /etc/tinc/linodeVPN.

6. Next, append the rsa_key.pub at the end of each host file. From the application server:

   sudo bash -c "cat /etc/tinc/linodeVPN/rsa_key.pub >> /etc/tinc/linodeVPN/hosts/appserver"
   

   From the database server run a similar command:

   sudo bash -c "cat /etc/tinc/linodeVPN/rsa_key.pub >> /etc/tinc/linodeVPN/hosts/dbserver"
   

Create VPN Control Scripts

Control scripts are responsible for setting up virtual interfaces on each server. They’re needed on both servers.

1. From the application server, create the following file to enable the tinc interface:

   File: /etc/tinc/linodeVPN/tinc-up

   1 2 3 4

   #!/bin/sh ip link set $INTERFACE up ip addr add 192.168.100.209 dev $INTERFACE ip route add 192.168.100.0/24 dev $INTERFACE

   Create a script to disable the interface:

   File: /etc/tinc/linodeVPN/tinc-down

   1 2 3 4

   #!/bin/sh ip route del 192.168.100.0/24 dev $INTERFACE ip addr del 192.168.100.209 dev $INTERFACE ip link set $INTERFACE down

2. Create a similar set of scripts on the database server:

   File: /etc/tinc/linodeVPN/tinc-up

   1 2 3 4

   #!/bin/sh ip link set $INTERFACE up ip addr add 192.168.100.130 dev $INTERFACE ip route add 192.168.100.0/24 dev $INTERFACE

   Add a shutdown script:

   File: /etc/tinc/linodeVPN/tinc-down

   1 2 3 4

   #!/bin/sh ip route del 192.168.100.0/24 dev $INTERFACE ip addr del 192.168.100.130 dev $INTERFACE ip link set $INTERFACE down

3. After creating the control scripts, you will need to change the permissions on both servers:

   sudo chmod -v +x /etc/tinc/linodeVPN/tinc-{up,down}
   

Create tinc Unit File

In order to run tinc as a service on startup, you’ll need to set up a systemd unit file for each server. Edit the following file on both the application and database servers.

File: /etc/systemd/system/tinc.service

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

[Unit] Description=Tinc net linodeVPN After=network.target [Service] Type=simple WorkingDirectory=/etc/tinc/linodeVPN ExecStart=/sbin/tincd -n linodeVPN -D -d3 ExecReload=/sbin/tincd -n linodeVPN -kHUP TimeoutStopSec=5 Restart=always RestartSec=60 [Install] WantedBy=multi-user.target

Host Files Interchange

At this point, you have configuration files created on each server. Because of tinc’s P2P nature, the last thing you need to do is interchange host files between nodes. There are many ways to accomplish this, but we’ll use scp here.

From the application server:

scp /etc/tinc/linodeVPN/hosts/appserver <user>@<dbserver>:/tmp/
ssh -t <user>@<dbserver> sudo mv -v /tmp/appserver /etc/tinc/linodeVPN/hosts/

From the database server:

scp /etc/tinc/linodeVPN/hosts/dbserver <user>@<appserver>:/tmp/
ssh -t <user>@<appserver> sudo mv -v /tmp/dbserver /etc/tinc/linodeVPN/hosts/

Test tinc

1. It’s time to test your newly configured VPN. Start the tincd daemon on the application server:

   sudo tincd -n linodeVPN -D -d3
   

2. Do the same on database server:

   sudo tincd -n linodeVPN -D -d3
   

   If everything was configured successfully, you should see an output similar to this:

   

3. You can open another terminal (i.e., from appserver) and check the active interfaces:

   sudo ip a
   

   You should have at least three interfaces, one of them your linodeVPN.

   Another quick test you can do is to ping the database server from the application server using its VPN address:

   ping 192.168.100.130
   

   If you encounter errors during your testing, you can add this flag to your daemon command:

   sudo tincd -n --logfile[=FILE] linodeVPN -D -d5
   

Complete Your tinc Configuration

Once you have your tinc VPN ready you can enable the service on startup:

sudo systemctl enable tinc.service

Now you can start, stop, restart, and check the service using common systemd syntax.

sudo systemctl status tinc.service

How to Deploy a Three-Node tinc mesh

This topology can be considered a variant of the single-node where a high traffic application requires separate instances to scale, resource optimization and faster response (asynchronous processing).

In the interest of showcasing tinc’s easy expandability, we’ll assume that LINODE1 and LINODE2 are the same application server and database server from the previous section.

The cheat sheet for this topology is:

1. Configure the new webserver (Linode 3). Follow the previously explained steps to install the tinc VPN and create the working directory.

2. The main configuration file for this instance would be:

   File: /etc/tinc/linodeVPN/tinc.conf

   1 2 3 4 5

   Name = webserver Device = /dev/net/tun AddressFamily = ipv4 ConnectTo = appserver ConnectTo = dbserver

3. Edit the host file:

   File: /etc/tinc/linodeVPN/hosts/webserver

   1 2	Address = 33.33.33.33 Subnet = 192.168.100.140

4. This time increase the security level on the encryption keys:

   sudo tincd -n linodeVPN -K 8192
   

5. Once again, you need to append the public key to the host file:

   sudo bash -c "cat /etc/tinc/linodeVPN/rsa_key.pub >> /etc/tinc/linodeVPN/hosts/webserver"
   

6. Add control scripts:

   File: /etc/tinc/linodeVPN/tinc-up

   1 2 3 4

   #!/bin/sh ip link set $INTERFACE up ip addr add 192.168.100.140 dev $INTERFACE ip route add 192.168.100.0/24 dev $INTERFACE

   File: /etc/tinc/linodeVPN/tinc-down

   1 2 3 4

   #!/bin/sh ip route del 192.168.100.0/24 dev $INTERFACE ip addr del 192.168.100.140 dev $INTERFACE ip link set $INTERFACE down

7. Change permissions:

   sudo chmod -v +x /etc/tinc/linodeVPN/tinc-{up,down}
   

8. The systemd unit file on this server will be identical to the previous servers:

   File: /etc/systemd/system/tinc.service

   1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

   [Unit] Description=Tinc net linodeVPN After=network.target [Service] Type=simple WorkingDirectory=/etc/tinc/linodeVPN ExecStart=/sbin/tincd -n linodeVPN -D -d3 ExecReload=/sbin/tincd -n linodeVPN -kHUP TimeoutStopSec=5 Restart=always RestartSec=60 [Install] WantedBy=multi-user.target

9. The last step is to interchange host files between all nodes. You will need to copy the application and database server’s host files to the web server, and web server’s host file to the application and database servers.

   From webserver:

   scp /etc/tinc/linodeVPN/hosts/webserver <user>@<appserver>:/tmp/
   ssh -t <user>@<appserver> sudo mv -v /tmp/webserver /etc/tinc/linodeVPN/hosts/
   
   scp /etc/tinc/linodeVPN/hosts/webserver <user>@<dbserver>:/tmp/
   ssh -t <user>@<dbserver> sudo mv -v /tmp/webserver /etc/tinc/linodeVPN/hosts/
   

   From appserver:

   scp /etc/tinc/linodeVPN/hosts/appserver <user>@<webserver>:/tmp/
   ssh -t <user>@<webserver> sudo mv -v /tmp/appserver /etc/tinc/linodeVPN/hosts/
   

   From dbserver:

   scp /etc/tinc/linodeVPN/hosts/dbserver <user>@<webserver>:/tmp/
   ssh -t <user>@<webserver> sudo mv -v /tmp/dbserver /etc/tinc/linodeVPN/hosts/
   

10. Finally, modify the tinc.conf file on appserver and dbserver. The new configuration files need to tell tinc to look for other nodes:

  
  




    

        
    
 
 

  File: /etc/tinc/linodeVPN/tinc.conf
 
 
 

  


1
2
3
4
5
Name = appserver
Device = /dev/net/tun
AddressFamily = ipv4
ConnectTo = dbserver
ConnectTo = webserver
File: /etc/tinc/linodeVPN/tinc.conf
1
2
3
4
5
Name = dbserver
Device = /dev/net/tun
AddressFamily = ipv4
ConnectTo = appserver
ConnectTo = webserver

11. Now you can start the tinc service on the webserver:

    sudo systemctl enable tinc.service
    sudo systemctl start tinc.service
    

Use tinc for Centralized Cloud Interconnection

This setup illustrates a use-case where regional branches need to interact with a centralized application such as inventory management software. In the last use case, you will configure a VPN with four Linode servers. Each server should be in a different geographic location.

The cheat-sheet in this case is:

After the previous two sections, you should be familiar with the configuration procedure:

1. Install tinc VPN on each node.
2. Create the VPN’s working directory on each node.
3. Create tinc.conf and host files on every node.
4. Create VPN control scripts for all tinc instances.
5. Create systemd unit files.
6. Exchange host files amongst all nodes.
7. Enable tinc systemd unit(s).

The configuration file tinc.conf on Linodes 1, 2, and 3 should point only to Linode HQ (ConnectTo). The configuration file on Linode HQ should define connections with all nodes using the same directive. The corresponding configuration files are:

Linode1:

File: /etc/tinc/linodeVPN/tinc.conf

1 2 3 4

Name = linode1 Device = /dev/net/tun AddressFamily = ipv4 ConnectTo = linodeHQ

Linode2:

File: /etc/tinc/linodeVPN/tinc.conf

1 2 3 4

Name = linode2 Device = /dev/net/tun AddressFamily = ipv4 ConnectTo = linodeHQ

Linode3:

File: /etc/tinc/linodeVPN/tinc.conf

1 2 3 4

Name = linode3 Device = /dev/net/tun AddressFamily = ipv4 ConnectTo = linodeHQ

The central server:

File: /etc/tinc/linodeVPN/tinc.conf

1 2 3 4 5 6

Name = linodeHQ Device = /dev/net/tun AddressFamily = ipv4 ConnectTo = linode1 ConnectTo = linode2 ConnectTo = linode3